Schottky diode suitable for power applications
Author: Shenzhen Yuan Zhi Electronics Co., Ltd.Time:2018-03-01 16:54:56Views:1832【SML】
As
North America does not have the PFC regulations in place, energy
savings and space / cost considerations are additional drivers that PFCs
must use in consumer products, computers, and communicat...
label:
As
North America does not have the PFC regulations in place, energy
savings and space / cost considerations are additional drivers that PFCs
must use in consumer products, computers, and communications. The
Schottky diode power factor correction (PFC) market is mainly affected
by global regulations related to reducing harmonic distortion. Schottky diodes in Britain, Japan and China also have similar standards. DCM
mode is typically used for applications with output powers between 75W
and 300W; CCM mode is used for applications where Schottky diodes output
power greater than 300W. When
the output power exceeds 250W, PFC is cost-effective, because of other
aspects (such as efficiency) has been compensatory increase. There are two general modes of active PFC: discontinuous current mode
(DCM) and continuous current mode (CCM) using delta and trapezoidal
current waveforms.
There
is a lower Rdson required when inputting a Schottky diode at 85Vac
because the conduction heat loss is inversely proportional to the 3rd
power of the input voltage. This high frequency MOSFET tube work can significantly reduce the boost suppression. Therefore, the transistor's fast switching characteristics are necessary. Schottky diode applications Boost diodes should have fast switching, low Vf and low Qrr characteristics. To reduce the peak current stress when the MOSFET is on, low Qrr is a must. Without this feature, the boost MOSFET will add temperature and Rdson, resulting in more power loss, which reduces efficiency. Efficiency
in high power density applications is a key factor in achieving smaller
volumes (30 W / cm 3 inches) and reducing the size of passive
components. Therefore, high switching frequency is essential.
In
order to design a CCM PFC with excellent efficiency and form factor,
the boost diode must also have Schottky diode applications with the
following features: Short reverse recovery and forward recovery time;
Small stored charge Q; Low leakage current vs. Low switching loss. Overvoltage
and inrush current capability is important as they can be used to
handle surges and overcurrent in PFC caused by startup and AC fallback. These features can only be achieved with silicon carbide Schottky diodes (SiC Schottky diodes).
The
Schottky diodes are easy to use because the switching behavior of SiC
Schottky diodes is independent of the forward current (Iload), switching
speed (di / dt), and Schottky diode temperature. SiC
Schottky diodes are used in the design to achieve large switching
frequency (up to 1MHz) allowing the use of smaller passive components.
2018-03-01
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